This invention relates to moisture detection.
As used herein the expression xe2x80x9cmoisturexe2x80x9d is to be given a broad meaning and refers to fluids, particularly water, in a porous medium and/or the solutes contained therein.
The invention has particular but not exclusive application to agricultural methods and apparatus for detecting when adequate irrigation has been applied to the soil and for illustrative purposes reference will be made to such application. However it will be appreciated that the invention may be utilised in other applications which involve the detection of moisture.
Devices which can assist irrigators to apply water in accordance with plant requirements are known. These include sensors based on electric, thermal and matric suction measurements (gypsum blocks, thermal probes, capacitance probes and tensiometry), and dielectric or radiation absorption measurements (time domain reflectometry, neutron scattering). These sensors vary in their cost, robustness, accuracy and the complexity of operation.
The present invention aims to provide an alternative to known methods and apparatus for moisture detection.
This invention in one aspect resides broadly in a method of detecting moisture within an unsaturated permeable medium, the method including:
distorting the flow streamlines within the unsaturated permeable medium to increase the fluid content at points therein, and
detecting the increased fluid content.
In another aspect this invention resides broadly in a detection assembly for detecting moisture within an unsaturated permeable medium, the assembly including:
streamline distortion means for distorting the flow streamlines within the medium to increase the fluid content at points therein, and
detection means for detecting the increased fluid content.
As used herein the expression xe2x80x9cflow streamlinexe2x80x9d refers to the trajectory followed by a fluid particle moving through a permeable medium.
In a preferred embodiment the detection means constitutes switching means for activating a circuit to generate a signal. The configuration of the streamline distortion means may be such that operation of the switching means within a predetermined time indicates a given moisture content within the unsaturated permeable medium.
It is preferred that the flow streamlines are distorted to cause saturation at points in the permeable medium and that the detection assembly includes collecting means for collecting free fluid from the saturated permeable medium.
As used herein the expression xe2x80x9cfree fluidxe2x80x9d means fluid which has a free boundary and which is able to be poured.
In a preferred embodiment the streamline distortion means includes a surface inclined to the flow streamlines within the permeable medium.
The streamline distortion means may thus have a variety of shapes and configurations and could for example be a planar surface, a sphere or a cylinder. In a preferred embodiment the streamline distortion means is a funnel and the collecting means includes a chamber located proximate the outlet of the funnel. Preferably the assembly includes vent means for venting the chamber, and suction means for generating a suction within the chamber.
In another aspect this invention resides broadly in an irrigation control assembly including:
a funnel;
a moisture detector located proximate the outlet of the funnel,
and indicating means for providing an indication that a given moisture content has been detected by the moisture detector.
The indicating means may generate an alarm or alternatively the indicating means may generate a signal to stop irrigation.
In a further aspect this invention resides broadly in a method of controlling irrigation, the method including:
locating a funnel in a medium to be irrigated;
detecting the presence of a given irrigating fluid content in the medium within the funnel or proximate the outlet thereof, and
ceasing the irrigation upon detection of the given irrigating fluid content.
In yet another aspect this invention resides broadly in a method of irrigating a crop planted in a planting medium, the method including:
locating streamline distortion means in the planting medium within or proximate the crop plant root zone, the streamline distortion means having a surface inclined to the flow streamlines in the planting medium;
detecting the presence of free irrigating fluid formed by the streamline distortion means;
generating a signal upon detecting the presence of the free irrigating fluid, and
ceasing irrigation in response to generation of the signal.
This invention also resides broadly in a method of nutrient scheduling and/or pollution monitoring within a permeable medium, the method including;
locating streamline distortion means in the medium, the streamline distortion means having a surface inclined to the flow streamlines in the medium;
detecting the presence of fluid formed by the streamline distortion means;
collecting the fluid, and
analysing the collected fluid.
This invention also resides broadly in a method of assessing drainage below the crop plant root zone of a crop planted in a planting medium, the method including:
locating streamline distortion means in the planting medium within or proximate the crop plant root zone, the streamline distortion means having a surface inclined to the flow streamlines in the planting medium;
detecting the presence of fluid formed by the streamline distortion means, and
measuring the time elapsed between initial detection of the presence of the fluid and cessation of detection of the presence of the fluid.
This invention also resides broadly in a method of controlling the rotation of crops planted in a planting medium, the method including:
locating streamline distortion means in the planting medium within and below the crop plant root zone, the streamline distortion means having a surface inclined to the flow streamlines in the planting medium;
detecting the presence of fluid formed by the streamline distortion means;
measuring the depth to which the fluid has penetrated, and
rotating the crops in accordance with the depth.
This invention also resides broadly in a method of delaying irrigation in accordance with rainfall, the method including:
locating a funnel in a medium to be irrigated;
detecting the presence of rainfall in the medium within the funnel or proximate the outlet thereof, and
controlling the irrigation in accordance with detection of rainfall.
In another aspect this invention resides broadly in a detection assembly for detecting moisture within an unsaturated permeable medium, the assembly including:
streamline distortion means for distorting the flow streamlines within the medium to increase the fluid content at points therein;
detection means for detecting the increased fluid content;
collecting means for collecting free fluid from the saturated permeable medium, and
vent means for venting the collecting means to a space within the detection assembly.
In a preferred embodiment the space is between the collecting means and a detection assembly housing.